While always-on Internet connections are widespread and various services have appeared accordingly, there is a demand to be able to receive such services in various places at home. Generally speaking, each home has a different home network configuration, and apparatuses used therein are various such as PCs, Internet appliances and the like. However, there is problem that connection settings or connection operations of Internet appliances are difficult for general users who do not have technical knowledge of such a network, and it is also difficult to establish a connection between apparatuses if a configuration of the network, such as a connection mode, router type or the like, is not taken into account.
In order to solve this problem, there is a technique called UPnP (Universal Plug and Play) stipulated by the UPnP Forum, which allows apparatuses within a home network to be interconnected.
By using UPnP, an apparatus within a home network can be automatically searched for and detected by multicasting, and an interconnection with the detected apparatus can be established.
FIG. 17A shows a home network comprising conventional UPnP apparatuses. In FIG. 17A, a modem having a router function, which is rented from an Internet service provider, is connected to a PC, a television and a VCR. FIG. 17B shows a process for detecting an apparatus by UPnP, which is performed in the case of operating the VCR from the PC.
In FIG. 17B, the PC first multicasts, on the network, an apparatus detection request which contains information indicating that a search target is the VCR (step S201). The apparatus detection request is received by all the UPnP apparatuses on the network, and each apparatus determines whether or not the search target is said each apparatus.
The VCR determines that the search target is the VCR, and transmits, to the PC which is a transmission source of the request, an apparatus detection response which contains necessary information for operating the VCR (step S202). By receiving the apparatus detection response, the PC is enabled to operate the VCR.
Using UPnP in this manner enables UPnP apparatuses to be interconnected.
In recent years, however, it has become common that a user connects a router having a wireless function, which the user has purchased, to a modem which functions as a router and which is rented from an Internet service provider, such that each router has apparatuses subordinately connected thereto as shown in FIG. 18A (hereinafter, this type of network configuration will be referred to as a router multistage configuration). FIG. 18B shows a process for detecting an apparatus by UPnP, which is performed when it is desired in FIG. 18A to control a VCR from a PC.
As shown in FIG. 18B, the PC first multicasts, on a network thereof, an apparatus detection request which contains information indicating that a search target is the VCR (step S301). The apparatus detection request is received by all the UPnP apparatuses on the network (a wireless router and a television T2 in FIG. 18A), and each apparatus determines whether or not said each apparatus is the search target.
Here, a general commercially available household router is configured, in consideration of security, so as not to transfer a multicast packet to another network. For this reason, in the router multistage configuration as shown in FIG. 18A, the wireless router does not transfer, to a private network N1, an apparatus detection request packet received from the PC. Therefore, the VCR which is the search target cannot receive the apparatus detection request, and does not return an apparatus detection response. Accordingly, an apparatus detection response reception waiting time-out occurs in the PC (step S302), and thus the apparatus detection fails (step S303).
As described above, in the router multistage configuration, an apparatus on the same network can be detected using UPnP multicasting. However, an apparatus on a different network cannot be detected.
Conventionally, there are a disclosed network connection apparatus and method (e.g., Patent Document 1) in which a plurality of networks, each of which is independently configured, are connected such that a plurality of devices on the respective networks can be interconnected.
According to the network connection apparatus and method of Patent Document 1, the plurality of networks, each of which is independently configured, are respectively provided with network connection apparatuses, and each network connection apparatus manages information about apparatuses on a corresponding network. The network connection apparatuses exchange such information each other, and this enables apparatuses on different networks to be interconnected.
FIG. 19A shows a router multistage home network in which gateways each including the network connection apparatus of Patent Document 1 are provided. It is assumed here that a network connection apparatus D1 has already obtained, as access information about a network connection apparatus D2, an IP address and a port number of a gateway G2, and the network connection apparatus D2 has already obtained, as access information about the network connection apparatus D1, an IP address and a port number of a gateway G1. FIG. 19B shows a process for detecting an apparatus by using the network connection apparatus and method of Patent Document 1, which process is performed in the case of operating a VCR from a PC in FIG. 19A.
As shown in FIG. 19B, the network connection apparatus D1 collects, by multicasting an apparatus detection request, information about apparatuses (television T1, VCR) on a private network N1 (step S401). Similarly, the network connection apparatus D2 collects, by multicasting an apparatus detection request, information about apparatuses (PC, television T2) on a private network N2 (step S402).
Next, the PC on the private network N2 transmits, to the network connection apparatus D2, an apparatus detection request which contains information indicating that a search target is the VCR (step S403). Upon receiving the request, the network connection apparatus D2 sets an IP address and a port number of the gateway G1 as a transmission destination, and then transfers the apparatus detection request to the network connection apparatus D1 (step S404). The network connection apparatus D1 searches the apparatus information obtained at step S401 for information about the VCR which is the search target contained in the received apparatus detection request, and transmits the information about the VCR to the network connection apparatus D2 as an apparatus detection response (step S405). Upon receiving the apparatus detection response, the network connection apparatus D2 transfers the response to the PC which is a transmission source of the request (step S406). In the above manner, the PC is enabled to operate the VCR which is on a different network.                [Patent Document 1] Japanese Laid-Open Patent Publication No. 2004-320741        